Extraction of compounds from dairy products
The present invention relates to processes for the treatment of dairy products and dairy process streams to produce lipids and substantially defatted protein streams. More specifically it relates to the use of near critical fluid extraction techniques to extract lipids from liquid dairy products and dairy process streams. Preferred solvents for use in the described near critical extraction techniques are ether based solvents that are partially miscible with water. A particularly preferred solvent for use in the invention is dimethyl ether.
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The present application is the U.S. National Phase of International Application PCT/NZ2004/000014, filed Jan. 30, 2004 and claims priority to New Zealand Patent Application No. 523920, filed Jan. 31, 2003.
INTRODUCTIONThe present invention relates to processes for the treatment of dairy products and dairy process streams to produce lipids and substantially defatted protein streams. More specifically it relates to the use of near critical fluid extraction techniques to extract lipids from liquid dairy products and dairy process streams.
BACKGROUNDIt is well known that dairy products and process streams are a complex mixture of proteins, lipids, sugars and minerals. At present, there are limited methods available for extracting and refining specific components from such streams, and the separation of lipids from proteins in whey-based streams is difficult.
Acid precipitation, heat precipitation, enzymic precipitation, centrifugal separation, membrane filtration and ion exchange are well known methods of separating out components from milk and milk by products. However, these methods are often not cost efficient and often do not produce the desired yields. Also, certain extraction processes must be done under conditions that irreversibly alter the physical properties of the separated components (for example the denaturation of proteins).
WO 91/14377 and WO 92/08363 describe the use of supercritical carbon dioxide and subcritical carbon dioxide for the partial extraction of lipids and fractional precipitation of proteins from dairy products and process streams respectively. However, lipid yields are low using these techniques, with both publications showing limited success and no extraction of useful phospholipids and sphingolipids.
It is therefore an object of the present invention to provide an improved or alternative process for extracting a range of lipids from dairy products and dairy process streams.
SUMMARY OF INVENTIONIn a first aspect, the invention broadly comprises a method for treating a dairy product or a dairy process stream comprising at least the steps of:
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- a) contacting said dairy product or dairy process stream with an ether based solvent that is partially miscible with water, said ether based solvent being at a near critical temperature and pressure, to produce a near critical fluid phase containing lipids;
- b) separating the near critical fluid phase from the dairy product or dairy process stream to produce a substantially defatted dairy product or dairy process stream; wherein the dairy product or dairy process stream has a moisture content of greater than 75%; and
- c) reducing the pressure of the near critical fluid phase to recover the lipids.
Preferably the solvent is gaseous at room temperature.
More preferably the solvent is dimethyl ether or a mixture of dimethyl ether and water at or below the solubility of water in dimethyl ether.
Preferably the dimethyl ether is at a pressure of at least the vapour pressure at the extraction temperature.
Preferably the dimethyl ether is at a temperature between about 10 degrees Celsius and about 70 degrees Celsius.
More preferably the dimethyl ether is at a temperature between about 40 degrees Celsius and about 60 degrees Celsius
Preferably the dairy product or dairy process stream is selected from whey based streams, milk fat by-products, milk and cream.
Most preferred dairy product or process streams useful according to the present invention may be selected from whey, whey protein concentrate retentates, whey protein isolate by-products, butter by-products, anhydrous milkfat by-products or lipid containing dairy effluents. The dairy product or process streams may be either liquid in their normal state, thawed from frozen, or reconstituted from powders.
Preferably the moisture content of the dairy product or process stream is greater than about 75% and less than about 99%.
More preferably the moisture content of the dairy product or process stream is between about 80 and 95%, most preferably between 85 and 90%.
Preferably the dairy product or dairy stream is contacted with the solvent in a continuous manner.
In a further aspect, the invention provides an extract from a dairy product or dairy process stream obtained by any of the above methods.
In yet a further aspect, the invention provides a substantially defatted dairy product or dairy process stream obtained by any of the above methods.
This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.
The invention consists in the foregoing and also envisages constructions of which the following gives examples.
Every substance has its own “critical” point at which the liquid and vapour state of the substance become identical. Above but close to the critical point of a substance, the substance is in a fluid state that has properties of both liquids and gases. The fluid has a density similar to a liquid, and viscosity and diffusivity similar to a gas. The term “supercritical” as used herein refers to the pressure—temperature region above the critical point of a substance. The term “subcritical” refers to the pressure—temperature region equal to or above the vapour pressure for the liquid, but below the critical temperature.
The term “near critical” as used herein encompasses both supercritical and subcritical regions, and refers to pressures and temperatures near to the critical point.
As noted above, dairy products and dairy process streams are a complex mixture of proteins, lipids, sugars and minerals. Useful lipids present in dairy products and dairy process streams include phospholipids and sphingolipids.
Near-critical fluids are useful solvents for lipids. Supercritical CO2 is known to be used to extract neutral lipids, but in combination with ethanol as a co-solvent, can also be used to extract some classes of phospholipids. Propane is known to be a solvent suitable for extracting neutral lipids and phospholipids.
DME has previously been used in the extraction of flavours and aromas from solid food materials (see Yano et al U.S. Pat. No. 4,069,351 and U.S. Pat. No. 4,136,065), lipids from raw egg yolk (Yano et al U.S. Pat. No. 4,157,404) and dried egg powder (Yano et al U.S. Pat. No. 4,234,619). In U.S. Pat. No. 4,157,404, Yano states that while lipids can be extracted from raw egg yolk (75% moisture content), the proteins are denatured. In U.S. Pat. No. 4,234,619; Yano states that proteins are not denatured if the egg yolk is dry, but the phospholipids can only be partially extracted.
We have found that the denaturation of protein obtained by DME extraction techniques can be reduced or eliminated by ensuring that the moisture content of the starting dairy product or dairy stream is greater than 75%; and that addition of water to the DME as a co-solvent, to account for water that is co-extracted with lipids, assists in the prevention of denaturation.
We have also found that the short contact times that result from the continuous process of the invention (between the solvent and the dairy product or dairy stream) minimises the denaturation of proteins obtained by DME extraction techniques.
The contact time is length of time that the dairy stream or dairy product is exposed to the solvent at near-critical conditions.
In a preferred embodiment of the invention, the dairy stream or dairy product is contacted with the solvent in a contacting device suitable for continuous processing, such as—but not limited to—a nozzle, static mixer or porous membrane contactor. Separation of the defatted dairy stream (or dairy product) and near-critical solvent thus may take place immediately after the contacting device, and the contacting time is thus of the order of seconds.
The treatment of dairy products and dairy streams with moisture contents greater than 75% in a continuous manner with short contact times enables the extraction of lipids (including phospholipids and sphingolipids), leaving an aqueous stream containing substantially defatted, soluble dairy proteins.
The desired temperature range, especially for dairy streams containing whey proteins, is about 40 to 60 degrees Celsius. Over this narrow range, it is known that whey proteins reversibly unfold in solution, and it is postulated that this unfolding enables the near critical solvent access to the lipids to enable extraction.
Operation outside the preferred region is possible but leads to lower yields and freezing of products for temperatures below the desired range, and to thermal denaturation of proteins for temperatures above the desired range.
The methods of the present invention produce both lipid extracts and substantially defatted aqueous protein streams. The lipid extracts can be used in, for example, health foods, dietary supplements, pharmaceuticals and cosmetics, while the depleted dairy product or dairy process stream (substantially defatted protein streams) may be used in, for example, dairy products (e.g. cheeses, cultured foods and beverages, ice-cream, chocolate), nutrition bars and baked goods.
The above describes some preferred embodiments of the present invention and indicates several possible modifications but it will be appreciated by those skilled in the art that other modifications can be made without departing from the scope of the invention.
EXAMPLES Method and Apparatus Extraction from Dairy SolidsThe apparatus for the extraction of dairy-based solids (especially whey protein concentrate (WPC) powder) at a pilot scale is shown in
The solvent was then recycled back to the pump via heat exchanger HX4, water trap WT1 and sub-cooler HX1 or HX5. Extract samples were taken at regular time intervals from valves EV1 and EV2 as appropriate. Extractions were carried out for 90-120 minutes.
Method and Apparatus—Extraction from Dairy Liquids
The 10 liter apparatus for the fractionation of liquid dairy components, especially whey protein concentrates (WPC) using CO2, dimethyl ether (DME) or propane is shown in
Water was added to the base of the vessel in some experiments to provide a ‘water pool’ for the WPC to spray into. As WPC was recovered through valve EV3, the solution pressure was reduced from the operating pressure to cylinder pressure. WPC solution was then recovered from the base of auxiliary collection vessel SV3, while DME that flashed off from the solution was recycled via valve RV3, and recompressed via compressor RC1. The lipids and some water were dissolved in the DME, and left the extraction vessel via an outlet near the top of the vessel, and then passed through valve BV1 to bypass the first separation vessel. The combined DME rich solution then passed through a back-pressure regulator BPR1, where the pressure was reduced to cylinder pressure (˜5-6 bar), and then through heat exchanger HX3 and into jacketed separation vessel SV2. The extract (lipids and water) was precipitated into this vessel. This extract was recovered at regular time intervals by further depressurisation through valve EV5 into an additional separator SV5 to avoid freezing of the extract, and then through valve VV5. The additional separator was found to be unnecessary for DME, due to the high water content of the extract. The bulk of the DME exited the top of SV2 and then passed through a coriolis mass flow meter FM1, cooler heat exchanger HX4 before being recycled back to MP1 via the water trap WT1. When CO2 was used, the intermediate separator SV1 was also used to enable two-stage fractionation of the extracts. Similarly, when ethanol was used as a co-solvent, separator SV5 was used to efficiently recover the ethanol, and flash off the propane or CO2 to the vent.
The liquid dairy components apparatus and method was modified according to the dairy component extracted, solvent used, and method of contacting between the liquid and solvent. Raffinate (defatted dairy component) was recovered by depressurisation to atmospheric through valve EXV1 when using CO2. For propane and DME, this resulted in excessive foaming of the raffinate as the solvent flashed off, and freezing of the protein stream, all of which caused protein denaturation, and so an additional separator was used. A static mixer was employed after the cross joint to provide better mixing between the DME, liquid dairy stream and water co-solvent. Vessel EX1 was converted to a countercurrent packed column by placing 12 mm stainless steel Pall rings on top of a liquid/gas distribution plate inside the vessel to form a randomly packed bed, and changing the inlet points for the solvent and liquid dairy stream to the bottom and top of the vessel respectively. The liquid raffinate was withdrawn from the base of EX1, and the solvent and extract phase from the top of EX1.
Results Example 1 Extraction of Dairy WPC SolidsThis example shows that the yield of lipids from dairy WPC solids is very low for all near-critical solvents, and thus extraction is generally more effective from liquid solutions. Whey protein concentrate powders with the composition 80.26% by mass protein, 6.83% by mass lipid, and a total solids content of 96.43% were extracted with the near-critical solvents carbon dioxide, propane, and dimethyl ether. Additional laboratory scale experiments were performed with dimethyl ether at elevated temperatures. The solvent, pressure, temperature, mass of solids used, mass of solvent used, and extract solids and lipid yields are given in table 1.
The lipid yields are very low and an increase in extraction temperature did not increase the extraction yield to desirable level.
Example 2 Extraction of Dairy WPC Liquids; 80% ProteinThis example shows that an ether based solvent miscible with water (in this case dimethyl ether) may be used as a solvent—with and without water as a co-solvent—for the extraction of lipids from liquid dairy WPC streams. Fresh whey protein concentrate containing 80.26% by mass protein, 6.83% by mass lipid, and a total solids content of 96.43% on a powder basis; and 21.45% solids on an as-received basis was extracted with supercritical carbon dioxide at 300 bar with and without ethanol as a co-solvent; near-critical propane with and without ethanol as a co-solvent; and dimethyl ether with and without water as a co-solvent. The solvent, pressure, temperature, mass of solids used, mass of solvent used, and extract solids and lipid yields are given in table 2.
The yield of lipid using DME without water as a co-solvent was very high, but the proteins were extensively dried and denatured; and could not be easily recovered from the extraction vessel as they became insoluble in water. The use of water as co-solvent at a reduced extraction temperature of 290 K reduced the lipid yield to 41.3%, but enabled a quantitative recovery of partially defatted protein in solution. The protein-rich raffinate stream recovered from the propane trial formed a long-lasting, vigorous foam. No lipids were extracted. When ethanol was used as a cosolvent with propane, the lipid yield increased from zero to 12.5%, but some ethanol was recovered in the raffinate protein-rich stream, and a sludge layer of denatured protein formed upon standing at room temperature in this stream. Supercritical carbon dioxide gave a lipid yield of only 1.6%. The use of ethanol as a co-solvent increased the lipid yield to 11.5%, but again resulted in a protein-rich raffinate stream containing some ethanol. A sludge layer of denatured protein formed upon standing at room temperature.
Example 3 Extraction of Reconstituted High-Fat Whey Protein Concentrate (WPC)This example shows the effect of solids concentration on the yield of lipids from high-fat retentates arising from the production of whey protein isolates by membrane filtration. High fat WPC solids with the composition 61.95% protein, 9.72% lipid, 3.04% moisture, balance lactose and ash was reconstituted with distilled and deionized water to solids (as received) concentrations of 7.2, 14 and 21% by mass, equivalent to protein and lipid contents of 4.52 and 0.78; 8.67 and 1.36; 13.01 and 1.36% by mass respectively. The reconstituted WPC liquids were extracted using the apparatus shown in
The lipid yield decreases as the solids concentration increases, and is almost zero when dry solids are used, as shown in example 1.
Example 4 Extraction of Reconstituted High-Fat NPC and Preparation of the Lipid Extract and Defatted Protein ProductsHigh fat WPC solids with the composition 61.95% protein, 9.72% lipid, 3.04% moisture, balance lactose and ash was reconstituted with distilled, deionized water to give the following liquid composition of 8.80% whey protein, 1.56% lipids, 13.56% total solids, balance distilled water. 56.4 kg of the reconstituted WPC was extracted with 474.2 kg of dimethyl ether at 323 K and a pressure of 42 bar in the continuous flow apparatus (
This example shows that pre-heating the WPC prior to contacting with dimethyl ether improves the fat extraction efficiency for high fat WPC produced by either ion exchange or nicrofiltration. High fat WPC obtained by spray drying the ultrafiltered by-product stream of whey protein isolate produced by ion exchange (WPC A); and high fat WPC obtained by spray drying the ultrafiltered by-product stream of whey protein isolate produced by microfiltration (WPC B) were reconstituted to 14% total solids. The dry basis composition of WPC A was 79.2% protein, 10.9% fat, 1.0% lactose, and 3.61% ash, and reconstituted basis was 10.97% protein, 1.5% fat, 0.1% lactose and 0.5% ash, balance distilled water. The dry basis composition of WPC B was 74.6% protein, 11.6% fat, 4.3% lactose and 3.6% ash; and reconstituted basis was 10.21% protein, 1.6% fat, 0.6% lactose, 0.5% ash, balance distilled water. Both reconstituted high fat WPC streams were processed in the apparatus shown in
6067.5 g of the reconstituted WPC B was extracted with 39.69 kg of dimethyl ether at 326 K and a pressure of 40 bar. 3100 g of water co-solvent was continuously added to the dimethyl ether to account for extraction of water from the whey protein concentrate. 2357.5 g of extract was recovered, which was then evaporated to dryness in a rotary vacuum evaporator to yield 86.1 g of lipid rich extract. The lipid content, equivalent to an 80% overall lipid yield, contained around 29% phospholipids. 6170 g of an aqueous raffinate stream rich in soluble defatted protein was continuously recovered from the extraction process, containing 10.05% protein and only 0.3% fat. WPC B is produced by a similar method to the high fat WPC used in examples 3 and 4: the percentage of lipid extracted has increased from 70% (example 4) to 80%.
Example 6 Extraction of Early and Late Season Beta-SerumBeta-serum is a phospholipid-rich stream derived from the production of anhydrous milkfat. The composition of this by-product stream is seasonally dependent. The proteins are predominantly casein proteins. In this example lipids are extracted from both fresh and thawed (from frozen) beta serum. Late-season beta-serum with a dry basis composition 30.91% protein, 21.38% lipid, balance lactose and ash was supplied fresh with a total solids content of 10.01%, including protein at 3.09% and lipids at 2.14%. Early season beta serum with a dry basis composition 30.5% protein, 19.5% lipids, 43.9% lactose and 6.1% ash was supplied frozen with a total solids content of 9.69%, including protein at 3.04%, fat at 1.95%, lactose at 4.39% and ash at 0.61%. Both beta serum liquid streams were extracted in the apparatus shown in
Frozen early season beta serum was thawed and then stirred at room temperature for 2 hours to obtain sample homogeneity. 7949.6 g of thawed early season beta serum was extracted with 80.45 kg of dimethyl ether at 322 K and a pressure of 40 bar. 3400 g of water co-solvent was continuously added to the dimethyl ether to account for extraction of water from the beta serum. 4333.5 g of extract was recovered, which was then evaporated to dryness in a rotary vacuum evaporator to yield 144.6 g of lipid rich extract. The lipid content was equivalent to a 93% overall lipid yield. 6598.2 g of an aqueous raffinate stream rich in defatted soluble protein was continuously recovered from the extraction process, containing 3.45% protein and only 0.50% fat.
Example 7 Extraction of Reduced Lactose Beta SerumIn this example, beta serum that was ultrafiltered to give a low lactose beta serum retentate (LLBS); and then diafiltered to give a very low lactose beta serum retentate (VLBS) were tested at approximately 20% solids concentration. The VLBS and LLBS were produced from the early season beta serum used in example 6. The composition of LLBS, dry basis, was 47.3% protein, 31.7% fat, 16.1% lactose and 4.9% ash. Frozen LLBS was supplied with 23.5% dissolved solids, including 11.1% protein, 7.45% lipids, 3.8% lactose and 1.15% ash. The composition of VLBS, dry basis, was 50.9% protein, 34.2% lipids, 9.9% lactose and 5.0% ash. Frozen VLBS was supplied with 20.18% dissolved solids, including 10.3% protein, 6.90% lipids, 2.0% lactose and 1.0% ash. Both beta serum liquid streams were extracted in the apparatus shown in
8834.0 g of VLBS was extracted with 95.04 kg of dimethyl ether at 323 K and a pressure of 40 bar. 3800 g of water co-solvent was continuously added to the dimethyl ether to account for extraction of water from the beta serum. 5622.6 g of extract was recovered, which was then evaporated to dryness in a rotary vacuum evaporator to yield 495.1 g of lipid rich extract. The lipid content was equivalent to a 74% overall lipid yield. The phospholipid content was 40% of total lipids. 5094.3 g of an aqueous raffinate stream rich in defatted soluble protein was continuously recovered from the extraction process, containing 11.93% protein and only 2.1% fat.
Example 8 Extraction of Reduced Lactose Beta Serum Diluted to 10% Dissolved SolidsIn this example, low lactose beta serum retentate (LLBS); and very low lactose beta serum retentate (VLBS) from example 7 were diluted to approximately 10% solids concentrations by adding distilled deionized water in the correct proportions to the respective thawed and stirred retentates. The diluted serum retentates are renamed LLBSD and VLBSD. The dry basis compositions of LLBSD and VLBSD are unchanged from example 7. LLBSD was produced with 11.1% dissolved solids, including 5.53% protein, 3.50% lipids, 1.5% lactose and 0.5% ash. VLBSD was produced with 9.26% dissolved solids, including 4.7% protein, 3.20% lipids, 0.9% lactose and 0.5% ash. Both beta serum liquid streams were extracted in the apparatus shown in
6885.9 g of VLBSD was extracted with 75.49 kg of dimethyl ether at 318 K and a pressure of 40 bar. 4150 g of water co-solvent was continuously added to the dimethyl ether to account for extraction of water from the beta serum. 5834.5 g of extract was recovered, which was then evaporated to dryness in a rotary vacuum evaporator to yield 226.0 g of lipid rich extract. The lipid content was equivalent to a 86% overall lipid yield. The phospholipid content was 46.5% of total lipids. 5362.6 g of an aqueous raffinate stream rich in defatted soluble protein was continuously recovered from the extraction process, containing 6.52% protein and only 0.5% lipid, with a phospholipid content of 47.9% of total lipids. There was a significant increase in lipid yield and reduction in residual lipids in the raffinate compared to VLBS in example 7.
Claims
1. A method for treating a dairy product or dairy process stream comprising at least the steps of:
- a) contacting a liquid dairy product or dairy process stream comprising a moisture content of greater than 75% with an ether based solvent that is gaseous at room temperature and that is partially miscible with water, said ether based solvent being at a near critical temperature and pressure, to produce a near critical fluid phase containing lipids;
- b) separating the near critical fluid phase from the dairy product or dairy process stream to produce a defatted dairy product or dairy process stream; and
- c) reducing the pressure of the near critical fluid phase to recover the lipids.
2. A method according to claim 1 wherein the solvent is at a temperature between about 10 degrees Celsius and about 70 degrees Celsius.
3. A method according to claim 1 wherein the solvent is at a temperature between about 40 degrees Celsius and about 60 degrees Celsius.
4. A method according to claim 1 wherein the dairy product or dairy process stream is selected from whey, milk fat, milk and cream.
5. A method according to claim 4 wherein the dairy product or dairy process stream is selected from the following: whey, whey protein concentrate retentates, whey protein isolate by-products, butter by-products, anhydrous milk fat by-products and lipid containing dairy effluents.
6. A method according to claim 1 wherein the dairy product or dairy process stream has been thawed from a frozen state.
7. A method according to claim 1 wherein the dairy product or dairy process stream has been reconstituted from powder.
8. A method according to claim 1 wherein the moisture content of the dairy product or dairy process stream is greater than 75% and less than about 99%.
9. A method according to claim 1 wherein the moisture content of the dairy product or dairy process stream is between about 80% and 90%.
10. A method according to claim 1 wherein the moisture content of the dairy product or dairy process stream is between about 85% and 90%.
11. A method according to claim 1 wherein the solvent is dimethyl ether.
12. A method according to claim 1 wherein the solvent is a mixture of dimethyl ether and water at or below the solubility of water in dimethyl ether.
13. A method according to claim 1 wherein the solvent is at a pressure of at least the vapour pressure of the solvent at the near critical temperature.
14. A method according to claim 1 wherein the dairy product or dairy process stream is contacted with the solvent in a continuous manner.
15. A method according to claim 1, wherein the solvent is at a pressure of at least 32 bar.
16. The method according to claim 1, wherein the lipids comprise phospholipids or sphingolipids.
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Type: Grant
Filed: Jan 30, 2004
Date of Patent: Apr 5, 2011
Patent Publication Number: 20060275533
Assignee: Fonterra Co-Operative Group Limited (Auckland)
Inventors: Andrew Fletcher (Palmerston North), Katrina Fletcher (Palmerston North), Owen Catchpole (Wellington), John Grey (Wellington)
Primary Examiner: Keith D Hendricks
Assistant Examiner: Hamid R Badr
Attorney: Knobbe Martens Olson & Bear LLP
Application Number: 10/543,446
International Classification: A23C 9/00 (20060101);